265A_HW2_Fall2005 - ECE 265A Homework #2 Due Wed. Nov. 30,...

ECE 265A Homework #2 Due Wed. Nov. 30, 2005 In-Class. No late homeworks accepted. 1)25 pts: Consider the current controlled attenuator discussed in class. An alternative to the current controlled single-diode “resistor” is the diode configuration in Fig. 1 where the dc current through the pair of equal-size diodes controls the value of the resistance. The diodes have been connected in “anti-series” configuration in the hope that the linearity will be “better.” What is the OIP3(V) of this anti-series pair diode transfer function (the transfer function is the small-signal voltage across the diodes as a function of the small-signal current through the diodes) as a function of the small-signal resistance to ground r ? How does this compare to the single diode configuration (also shown in Fig. 1) with the same value ofr?Compare the two OIP3s for the specific cases of r=50. Hint: perform a series reversion to get an expression for the diode voltage as a function of current. Then add the two diode voltages to get the total voltage, assuming each has the same current. Watch for the sign conventions!

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